JPH0476257A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To ensure smooth operability of a piston and make the piston light- weight by forming a crown and skirts as separate parts, and forming land parts fitting into ring grooves of the crown integrally on the upper ends of the skirts made of metal plates to connect both the parts to each other. CONSTITUTION:The piston 1 consists of a crown 6 which has a top face 2 confining a combustion chamber and ring grooves 3, 4, etc. for holding piston rings, and ring-shaped skirts 7, as separate parts, slidably contacting a cylinder. The skirts 7 are formed into a specified shape using rolled steel plates, and have right and left skirt parts 11, 12 slidably contacting the cylinder wall, and land parts 13 fitting into the ring grooves 3, 4. After the upper ends of the skirts 7 are fitted on the outer periphery of the crown, the land parts 13 are drawn along the ring grooves 3, 4 to form the cross-section into projected and recessed shapes bent along the ring grooves 3, 4, and are fitted on the full length of the peripheries of the ring grooves 3, 4.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in pistons for internal combustion engines.

(Prior Art) In order to increase the output of fils, it is important to reduce the weight of the piston and improve its operability.

For this reason, conventionally, a crown having a top surface defining a combustion chamber and a skirt that slides on the cylinder are formed separately from each other, and the skirt is made of, for example, fiber-reinforced resin to reduce the weight of the piston. It was proposed that the restrictions on the shape of the crown and skirt be reduced to reduce the number of 7 ricks (58-1 Utility Model).
(See Japanese Utility Model Application Publication No. 80352, Japanese Utility Model Application Publication No. 1988-194148, etc.).

(Problem to be Solved by the Invention) However, in such conventional devices, the upper end of the skirt is cast or fitted to the crown, so the bonding strength of the skirt to the crown is insufficient. , there was a concern that a scuff phenomenon would occur or that the piston ring would hit one side.

The present invention aims to solve one of these conventional problems.

(Means for solving the problem) In order to achieve the above object, in the present invention, a crown having a ring groove on which a piston ring is attached together with a top surface defining a combustion chamber, and a skirt that slides in contact with a cylinder are separated from each other. The skirt was made of a metal plate, and a land portion was formed at the upper end of the skirt to fit into the puffer groove of the crown to connect the two.

(Function) The reaction force that the skirt receives from the cylinder wall is supported by the land that fits into the ring groove with respect to the crown. Since the land portion has an uneven cross section that bends along the ring groove and is fitted over the entire circumference of the ring groove, sufficient bonding strength of the skirt to the crown is ensured.

In addition, since the ring groove of the crown is covered by a skirt, by forming the skirt from a steel plate, for example,
Sufficient wear resistance is ensured for the piston ring, and there is no need to perform surface hardening treatment on this part, increasing productivity.

(Example) Hereinafter, an example of the present invention will be described in 5. based on the accompanying drawings.

As shown in FIGS. 1 and 2, a piston 1 includes a crown 6 having a top surface 2 defining a combustion chamber, ring grooves 3 and 4 for housing piston rings, and an annular skirt in sliding contact with the cylinder. 7 are formed separately from each other ν1.

The crown 6 is formed by casting a light metal such as an aluminum alloy, but it is reinforced internally according to the required strength.
It is also possible to cast L fiber.

Further, a pair of bottle boss portions 9 for supporting a piston pin (not shown) are integrally formed on the crown 6, and a cooktop is connected to the crown 6 via the piston pin.

The skirt 7 is formed from a rolled steel plate into a predetermined shape.
The left and right skirt parts 11.12, which have left and right skirt parts 11.12 that slide on the cylinder wall and land parts 13 that fit into the ring grooves 3 and 4, are located on the sides of the piston pin and are formed to have an arcuate cross section. , controls the attitude of the piston 1 by slidingly contacting the cylinder wall.

The land portion 13 is formed by fitting the upper end of the skirt 7 formed into a right cylindrical shape to the outer periphery of the crown 6, and then inserting the ring grooves 3, 4 into the ring grooves 3, 4.
The cross section is drawn along the ring grooves 3 and 4.
The ring groove 3 is formed into an uneven shape that bends along the ring groove 3,
It fits all around the 4. After the land portion 13 is fixed by caulking, finishing is performed to ensure a predetermined accuracy with respect to the cylinder wall and piston ring.

A concave portion 14 is formed in an arc shape along the lower end of the crown 6 between the land portion 13 and the left and right skirt portions 11.12 to ensure the rigidity of the skirt portion 11.12 and to avoid unnecessary contact with the cylinder wall. Reduce area.

Furthermore, the skirt portion 11.12 is press-molded with unevenness (not shown) that limits the area that contacts the cylinder wall.
7 by ensuring rigidity and controlling the pressure distribution of the oil film.
It is also possible to reduce the friction.6 Next, the effect will be explained.

The piston 1 reciprocates within the cylinder in response to combustion gas pressure, which is converted into rotational motion of the crankshaft via a piston pin and connecting rod.

Combustion heat received at the top surface 2 of the piston 1 is released to the cylinder wall via the crown 6, skirt 7 and piston ring.

When the piston 1 reciprocates, a load that tends to tilt the piston 1 relative to the cylinder due to gas pressure and inertia acts in the thrust and anti-thrust directions perpendicular to the piston pin, but the skirt 7 slides against the cylinder wall. The piston 1 is kept coaxial with the cylinder, thereby preventing uneven contact of the piston ring and occurrence of slap noise.

Since the skirt 7 is made of a steel plate, the left and right skirt parts 11 and 12 can be elastically deformed, which prevents the lubricating oil film formed at the opening between the cylinder wall and the cylinder wall from breaking, and also prevents the shock generated when the cylinder wall opens. , and smooth movement of the piston 1 is ensured.

The reaction force that the left and right skirt parts 11 and 12 receive from the cylinder wall is caused by the reaction force that the left and right skirt parts 11 and 12 receive from the land part 1 that fits into the ring grooves 3 and 4 of the crown 6.
Supported by 3. The cross section of the land portion 13 has the ring groove 3,
Since the skirt 7 has an uneven shape that fits over the entire circumference of the crown 6, sufficient bonding strength of the skirt 7 to the crown 6 is ensured. On the other hand, with the conventional device in which the upper end of the skirt is cast into the crown, there is a problem that stress concentration occurs at the root portion of the skirt, and sufficient bonding strength cannot be obtained. Further, in the case of a conventional device in which the fitting portion of the skirt to the crown is formed in a right cylindrical shape and does not have a portion that engages in the axial direction, there is a fear that the two may separate due to differences in thermal expansion or the like.

By covering the ring grooves 3 and 4 with the skirt 7 made of a steel plate, high surface hardness is obtained at the portion that contacts the piston ring, and sufficient wear resistance is ensured. Thereby, there is no need to perform surface hardening treatment on the aluminum alloy crown 6, and productivity can be increased.

Generally speaking, the piston scuff phenomenon occurs at the skirt portion 11.12.
This occurs due to the land located between the ring W13.4 and the ring W13.4, but by using steel as the material of the skirt 7, the surface roughness accuracy of this land can be increased, which improves the ability to retain the lubricating oil film. This prevents the lubricating oil film from breaking and causing scuffing.

Next, another embodiment shown in FIGS. 3 and 4 will be explained.
Left and right beam portions 21 and 22 extending toward the left and right beam portions 1' and 12 are integrally formed, and the left and right skirt portions 11 and 22 are integrally formed.
．． The lower end of 12 is fixed.

In this case as well, since the land portion 13 that fits into the ring groove 3° 4 is provided at the upper end of the skirt 7, the left and right skirt portions 11.12 are supported by the crown 6 at their upper and lower ends to increase their rigidity. , it can respond to higher engine output.

(Effects of the Invention) As described above, according to the present invention, in a piston for an internal combustion engine, the crown having the top surface defining the fl combustion chamber and the ring groove in which the piston ring is mounted, and the skirt slidingly contacting the cylinder are mutually connected to each other. This skirt is formed from a metal plate, and a land portion that fits into the ring groove of the crown is integrally formed on the upper end of the skirt to connect the two, thereby ensuring smooth operation of the piston. It is possible to reduce the weight of the F91 engine, improve the output and fuel efficiency of the F91 engine, and reduce the surface treatment of the piston, increasing productivity and suppressing cost increases.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a piston showing an embodiment of the present invention, and FIG. 2 is a perspective view thereof. FIG. 3 is a cross-sectional view of a piston showing another embodiment, and FIG. 4 is a perspective view thereof. 1... Piston, 2... Top surface, 3, 4... Ring groove, 6... Crown, 7... Skirt, 11.12
...Skirt part, 13...Land part 9

Claims (1)

[Claims] A crown having a top surface that defines a combustion chamber and a ring groove for mounting a piston ring, and a skirt that makes sliding contact with the cylinder are formed separately from each other, and this skirt is formed of a metal plate, and a crown is provided at the upper end of the skirt. A piston for an internal combustion engine, characterized in that a land portion that fits into a ring groove is integrally formed to connect the two.